Type 2 diabetes diagnosis from a single blood sample ‘accurate’

A single blood sample may be sufficient to diagnose type 2 diabetes in clinical practice, an American study has claimed.

A positive result for glucose and HbA1c in a single blood sample is a “highly accurate” predictor of the condition and of its complications, including kidney disease and heart disease.

That is according to new research led by researchers at Johns Hopkins Bloomberg School of Public Health and published in the journal Annals of Internal Medicine.

Study lead author, Dr Elizabeth Selvin said: “The results of our study suggest that the two tests from one blood sample can provide adequate confirmation of diabetes, potentially allowing a major simplification of current clinical practice guidelines.

“Doctors are already doing these tests together – if a patient is obese, for example, and has other risk factors for diabetes, the physician is likely to order tests for both glucose and HbA1c from a single blood sample,” Selvin says. “It’s just that the guidelines don’t clearly let you use the tests from that one blood sample to make the initial diabetes diagnosis.”

The researchers examined data from a long-running Atherosclerosis Risk in Communities (ARIC) study, which has tracked the health of 13,000 Americans.

The study, begun in the late 1980s, was designed to find risk factors for atherosclerosis, a major underlying feature of heart disease and stroke, but in tracking the overall health of participants for decades it has gathered data relevant to diabetes, including blood glucose and HbA1c test results.

A total of 383 people were identified who, at their second study checkup in the early 1990s, did not have a diabetes diagnosis but did have positive results for both blood glucose and HbA1c from a single blood sample. Then 90 per cent went on to be diagnosed with diabetes during the first 15 years of the study (99 per cent by 20 years). These individuals also developed diabetes complications, such as heart disease, at much higher rates than individuals who did not have diabetes or who only had one elevated test result, the study found.

Dr Selvin added: “The bottom line is that this combination of positive results from a single blood sample has a very high positive predictive value for a subsequent diagnosis of diabetes, and also indicates a high risk of typical diabetes complications.”

Some people in the study who had positive results on only one test went on to be diagnosed with type 2 diabetes.